An introduction to the concept of SDR. This is a xtal-controlled receiver using the PC sound card so the basebandwidth will depends on what soundcard sampling rate your PC has. Simple to build and works with the Softrock type of applications (Winrad etc.). Choose the xtal or xtals to suit the band required. The design as-is is intended for the 80 meter amateur band so if you change the xtals for a different band you will also need to rework the antenna filter to suit. Layout isn't especially critical (for the lower frequencies at any rate).